Wednesday, January 13, 2016

Despite What You May Have Heard About The 1st Zika Case In The US . . .

Aedes Mosquito Ranges In the United States

#10,883

. . . yesterday's widely reported `1st case' (in Harris County, Texas) is far from the first Zika infected traveler to arrive in the United States. Yet somehow that narrative has made it all the way from local media reports to appearing in the prestigious BMJ (British Medical Journal) News this morning:

A
traveler who had recently returned from Latin America to Texas has had
Zika virus infection diagnosed, the first case to be recorded in the
United States, local health officials report. The case was identified in
Harris County, Texas, which includes the city of Houston.

Umair
A Shah, executive director of Harris County Public Health and
Environmental Services, warned travelers that Zika virus can now be
found in much of the world. “We encourage individuals traveling to areas
where the virus has been identified …

Officials in Harris County confirmed the case
Monday. It's not the first time a tourist has carried Zika to the U.S.,
the Centers for Disease Control and Prevention says. And Zika is not
poised to spread across the country just yet, but some experts are
worried.

This was the first instance where sexual transmission of an Arbovirus was suspected, the author’s writing:

Results
also support ZIKV transmission from patient 1 to patient 3. Patient 3
had never traveled to Africa or Asia and had not left the United States
since 2007. ZIKV has never been reported in the Western Hemisphere.
Circumstantial evidence suggests direct person-to-person, possibly
sexual, transmission of the virus.

Since then there have been at least twenty imported cases of Zika reported in the United States. Given that most people infected experience mild or subclinical symptoms, the real number is undoubtedly much higher.

It generally takes multiple introductions by viremic travelers, but as we saw with the introduction of Chikungunya to the Caribbean in late 2013, and Zika to Brazil in 2014, when the conditions are right, the virus can get a foothold and spread rapidly.

Mosquito borne viruses are viewed as a big enough emerging threat to the United States that last year, theCDC’sGrand Rounds, featured a presentation (now archived) called:

We see hundreds of imported cases of mosquito borne diseases in the United States each year – each with at least the potential
to seed local mosquito populations with the virus – but so far locally
acquired cases have remained rare.

But given the availability of two competent mosquito vectors (Aedes Aegypti & Aedes Albopictus),
and repeated introductions of the virus from travelers coming from
regions where the virus is endemic, our luck in this matter probably won't last
forever.